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Largest Cherenkov telescope ever sees first light

Looking into the depths of the universe. The five H.E.S.S. mirror telescopes in Namibia. (Picture: H.E.S.S. collaboration)

FAU scientists make substantial contribution to installation and data analysis

With the H.E.S.S. II telescope in Namibia the largest Cherenkov telescope ever has now started operation. Physicists from the Erlangen Centre for Astroparticle Physics (ECAP) and the Physics Institute at FAU were part of the international group of scientists who achieved this breakthrough.

The H.E.S.S. II telescope on the African continent, the largest of a total of five telescopes, will record the most powerful and extreme phenomena of the universe in very high–energy gamma-rays. The researchers hope to gain a deeper understanding of known high-energy cosmic sources such as supermassive black holes, pulsars and supernovae, as well as insights into new classes of high–energy cosmic sources.

FAU physicists are particularly interested in how the fragments of star explosions in our galaxy radiate in gamma light. “With H.E.S.S. II, we also want to improve our understanding of the ‘dark matter’ that surrounds us in massive amounts but the properties of which are literally still in the dark,” says Prof. Dr. Christoph van Eldik who coordinates the H.E.S.S. activities at ECAP with Ira Jung and Kathrin Valerius. The Erlangen group makes a central contribution to the H.E.S.S. experiment, for instance by developing the software for data collection and analysis, the calibration of the recorded data and the high–precision alignment of the telescopes. FAU scientists also installed the majority of the H.E.S.S. II’s 875 mirrors at the site in Namibia–some of them at breathtaking heights.

Installation at breathtaking heights. The surface area of the H.E.S.S. mirror is equivalent to two tennis courts. (Picture: H.E.S.S. collaboration)

At 600 tons in weight with a 28 metre mirror—the equivalent surface area of two tennis courts—the new telescope called H.E.S.S. II is gigantic. It first ‘saw light’ on 26 July 2012 at 00:43, when it took its first picture of atmospheric particle cascades generated by cosmic gamma rays and by cosmic radiation. This constitutes a decisive step forwards in the exploration of the Southern sky at gamma-ray energies.

Astrophysicists believe gamma rays to be produced by natural cosmic particle accelerators such as supermassive black holes, binary stars, pulsars, clusters of galaxies, supernovae and maybe even relics of the Big Bang. The universe is filled with these natural cosmic accelerators impelling charged particles such as electrons and ions to energies far beyond those that human-built particle accelerators reach. As high-energy gamma rays are secondary products of these cosmic acceleration processes, gamma ray telescopes allow us to study these high-energy sources. Today, well over one hundred cosmic sources of very high-energy gamma rays are known. With H.E.S.S. II, processes in these objects can be investigated in much greater detail. The researchers also expect that many new sources and classes of sources will be detected.